Strange that you've correctly identified that a "unique & specialist job" would more than double your salary, yet you make a point of saying you don't want one

Strange that you've correctly identified that a "unique & specialist job" would more than double your salary, yet you make a point of saying you don't want one of those. In other words, you have all the information you need in that paragraph you wrote to double your salary, but you don't seem interested in doing so. Why is that? There are lots of specialties, most of which are quite easy to become an expert in. Some of which can be accomplished simply by describing yourself to your next potential employer as a "___ specialist". If you're smart enough to have learned to program computers for a living, you're probably smart enough to learn to program (for example) iPhones for a living. I'd say that's a much better idea than describing yourself as an "employed developer" and seeking out the sort of place that pays market average wages for average people.